This invention relates to electronic calculators of a size small enough to be held in one hand and still having a sufficiently large keyboard capable of convenient operation with the fingers of the other hand. Conventional calculators of this size are generally too unwieldy to be conveniently carried in one's pocket. Thus it is customary to supply with each purchase of such small finger operable calculator a case with a strap for hand carrying the instrument.
The unwieldiness for pocket carrying of such conventional small finger operable electronic calculators is due primarily to several undesirable inherent physical characteristics. One of these undesirable inherent physical characteristics for pocket carrying of such conventional small electronic calculators is that their structure requires a rigid body or housing for providing a protective enclosure for the electronic circuitry and to provide a rigid base for supporting the mechanical elements such as the finger operable keyboard, function switches, readout register, and battery storage. Such rigid housing lacks the capacity to conform to one's body contour at the pocket in which the calculator is carried and thus tends to irritate or chafe one's body at the point of contact with the calculator housing.
Another of the undesirable physical characteristics for pocket carrying of most of such small conventional electronic calculators is that to accomodate the bulk of conventional finger operable keyboards, function switches, batteries, and readout register, their thickness is generally about one inch or more which thereby produces an undesirable bulge to the pocket in which it is carried, a bulge which makes it particularly unsuitable for breast pocket storage.
A further undesirable physical characteristic for pocket carrying of most such conventional small finger operable calculators is that of their weight. The cumulative weight of the rigid housing, conventional finger operable keyboard, readout register, function switches, and particularly the conventional batteries which are generally of size AA for powering the calculator result in a total weight of about one half pound or more which is greater than is convenient or comfortable for carrying in one's pocket over an extended period of time.
While smaller and lighter electronic calculators do exist, they are generally too small for convenient operation in that the keyboard is too small for convenient finger operation and generally requires an instrument such as a stylus to reach individual keys. As a result, numbers, both on the individual keys and at the readout register, are generally too small for the average person to readily identify without the aid of a magnifying glass. Also to retain their diminutive size, miniature battery cells, such as used to power wrist watches, are used as the power source and result in an undesirably short operating life of such calculators.
The present invention constitutes a significant advance in the art in that the above undesirable physical characteristics of conventional small electronic calculators have been overcome in Applicants' present invention which achieves a finger operable calculator structure which lends itself to a body thickness as small as a mere five thirty seconds of an inch to thereby permit convenient storage in even a breast pocket without producing a disfiguring bulge. Besides lending itself to such desirably thin construction, Applicants' present invention achieves a calculator structure which has physical body flexibility sufficient to resiliently conform to body contour at the position of the pocket in which it is carried and to resiliently bend rather than break under bending moment loads while still maintaining sufficient stiffness and size of number and function keys and readout register numbers and symbols to achieve easy finger operation and visual indentification of individual keys and readout register numbers and symbols.
Also Applicants' present invention achieves a calculator structure which lends itself to very long operating life with a single battery, and is highly suitable for including as an integral part of a thin, flexible pocket folder with accompanhing note pad or checkbook or bank deposit and withdrawal memorandum pad to thereby make possible "on-the-spot" computation of such commonly encountered problems as market list cost and bank deposit, withdrawal and interest effect on principal. It also lends itself to unobtrusive inclusion as an additional page in a student's or business man's conventional note book or as part of the note book's cover for ready access in making computations of mathematical problems encountered in the classroom, laboratory or in business.
A primary object of the present invention is the provision of an electronic calculator structure which has a sufficiently large keyboard capable of convenient operation with one's fingers and yet small enough and thin enough to be stored in even one's breast pocket without producing a significant pocket bulge.
Another object of the present invention is the provision of a finger operable electronic calculator structure which has sufficient physical resilience to conform to body contour at the position of the pocket in which it is carried and to bend rather than break under accidental bending moments encountered in normal use and incorporates sufficient stiffness for easy finger operation of function and number keys and general manual handling of the instrument.
A further object is the provision of a finger operable electronic calculator structure which even with a battery is extremely light in weight and has a long battery operational life.
And another object is the provision of a finger operable electronic calculator structure which lends itself to incorporation in a thin flexible pocket folder with memorandum pad for "on-the-spot" computation of mathematical problems.
And a still further object is the provision of a finger operable electronic calculator structure which lends itself to unobtrusive inclusion as an additional page or in the cover of a permanently bound or loose leaf notebook for convenient "on-the-spot" computations as mathematical problems are encountered.
And a still further object is the provision of a finger operable electronic calculator which is extremely thin, light in weight and resiliently flexible, which may be comprised of inexpensive commercially available components with only slight physical alteration to achieve the present invention.
And another object is the provision of a very thin, flexible finger operable electronic calculator structure which lends itself to a wide variety of functional complexities, from simple addition and subtraction to complex mathematical operations and memory storage and retrieval functions.